Year	Age
1970	4.3
1971	4.5
1972	4.8
1973	5
1974	5.3
1975	5.5
1976	5.8
1977	6.1
1978	6.4
1979	6.6
1980	6.9
1981	7.2
1982	7.5
1983	7.8
1984	8
1985	8.3
1986	8.6
1987	8.8
1988	9.1
1989	9.3
1990	9.5
1991	9.8
1992	10
1993	10.2
1994	10.5
1995	10.7
1996	10.9
1997	11.1
1998	11.3
1999	11.5
2000	11.7
2001	11.8
2002	12
2003	12.2
2004	12.3
2005	12.5
2006	12.6
2007	12.8
2008	12.9
2009	13